v.what.vect - Uploads vector values at positions of vector points
to the table.
vector, sampling, database, position, querying, attribute table
v.what.vect
v.what.vect --help
v.what.vect map=
name [
layer=
string]
column=
name query_map=
name
[
query_layer=
string]
query_column=
name
[
dmax=
float] [--
help] [--
verbose]
[--
quiet] [--
ui]
- --help
-
Print usage summary
- --verbose
-
Verbose module output
- --quiet
-
Quiet module output
- --ui
-
Force launching GUI dialog
- map=name [required]
-
Name of vector points map for which to edit attributes
Or data source for direct OGR access
- layer=string
-
Layer number or name
Vector features can have category values in different layers. This number
determines which layer to use. When used with direct OGR access this is
the layer name.
Default: 1
- column=name [required]
-
Name of attribute column to be updated with the query result
- query_map=name [required]
-
Name of vector map to be queried
Or data source for direct OGR access
- query_layer=string
-
Layer number or name
Vector features can have category values in different layers. This number
determines which layer to use. When used with direct OGR access this is
the layer name.
Default: 1
- query_column=name [required]
-
Name of attribute column to be queried
- dmax=float
-
Maximum query distance in map units (meters for ll)
Default: 0.0
v.what.vect transfers attributes from the
query_map’s map
attribute table into the attribute table of points present in the
map
map. The script is based on
v.distance.
The upload
column, into which the query results are stored, must be
present in the
map map. Use
v.db.addcolumn to add one if needed.
Use dmax parameter to control query distance tolerance (how far points/centroids
can be from
query_map features). For more options, use
v.distance instead.
In case of a multipoint input
map map, with several points having the
same category number, it can happen, that the query result is NULL, if the
same category number falls into different
query_map polygons.
When transferring attributes from a point map to a polygon map, usually
dmax has to be larger than zero (determined by distance between query
points and polygon centroids).
In case that one or both input vector maps are 3D, features need to touch also
in the 3rd dimension (z coordinate) in order to transfer attributes.
In this example, the ’hospitals’ point map in the North Carolina
location is copied to the current mapset, a new attribute column is added and
the urban names from the ’urbanarea’ polygon map are transferred
to the ’myhospitals’ map at the hospital points’
locations:
g.copy vect=hospitals,myhospitals
v.db.addcolumn myhospitals column="urb_name varchar(25)"
v.what.vect myhospitals query_map=urbanarea column=urb_name query_column=NAME
# verification:
v.db.select myhospitals
In this example, city names, population data and more from Geonames.org country
files are transferred to selected EU CORINE landuse/landcover classes
("Continuous urban fabric", 111, and "Discontinuous urban
fabric", 112). Note: Example in UTM projection to which the input maps
have been projected beforehand to have metric distances support:
# extract populated places from geonames
v.extract geonames_IT where="featurecla=’P’" output=geonames_IT_cities
# add new column
v.db.addcol corine_code111_112_cities column="gnameid double precision"
# transfer geonameid (3000m maximal distance between points and centroids)
v.what.vect corine_code111_112_cities query_map=geonames_IT_cities column=gnameid \
query_column=geonameid dmax=3000
# now gnameid can be used for v.db.join to join further
# attributes in from geonames.org
v.db.addcolumn, v.db.select, v.distance,
v.rast.stats, v.what.rast, v.what.rast3,
v.vect.stats
Markus Neteler
Last changed: $Date: 2016-08-22 04:16:33 +0200 (Mon, 22 Aug 2016) $
Available at: v.what.vect source code (history)
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